My Yeti has Amundsen+ radio, so (I assume) the roof aerial takes care of the AM/FM & GPS.   Is the roof aerial for units with DAB different, and if so are they easily retrofittable?   Or do I just need to run a cable?   At the moment, the performance of the Alpine windscreen mounted DAB aerial falls short of the previous Pure exernally (glass) mounted one that I used, but I'd rather not install that again if possible